I need to put Adafruit to sleep in order to conserve battery. I've searched the net for solutions withAdafruit feather 32u4 FONA andAdafruit RTC FeatherWing RTC moduleRumour has it that it should be possible to put the 32u4 to sleep and wake it up with a hardware interrupt from the RTC.Anyone has any info on this?

// Demonstrates power down mode. // Sketch will put Arduino to sleep when sleepPin is HIGH// Arduino will wake when sleepPin goes low// You can use any external interrupt pin for sleepPin:// See http://arduino.cc/en/Reference/AttachInterrupt for pin// and interrupt number information.// Written by Rick Lesniak for Adafruit Industries

#include <avr/sleep.h>

#define ledPin 13 /* Attach a LED and resistor to this pin. LED is on when Arduino is awake, off when sleeping */#define sleepPin 2 /*must be an external interrupt pin */

I have the RTC set to send a pulse on the INT every 20 seconds using Timer A. I set up an interrupt counter program and have verified that the interrupt pulses are being sent to pin 0. I then inserted the code that adafruit_support_rick posted and changed the sleepPin to 0. When I run the program my feather Fona will go to sleep but I never see the LED come back on so I am assuming that it is not waking back up. I am probably missing something obvious. Any thoughts?

// Demonstrates power down mode. // Sketch will put Arduino to sleep when sleepPin is HIGH// Arduino will wake when sleepPin goes low// You can use any external interrupt pin for sleepPin:// See http://arduino.cc/en/Reference/AttachInterrupt for pin// and interrupt number information.// Written by Rick Lesniak for Adafruit Industries// PCF8523 timer code borrowed from https://github.com/radikalbytes/PCF8523/blob/master/PCF8523.cpp

#include <avr/sleep.h>#include <Wire.h>

// for clock and timer control#include <PCF8523.h> //library with Timer A countdown built inPCF8523 rtc;//Use pin0 as wake up pine#define PCF8523_ADDRESS 0x68#define PCF8523_TMR_CLKOUT_CTRL 0x0F#define PCF8523_TMR_A_FREQ_CTRL 0x10#define PCF8523_TMR_A_REG 0x11#define PCF8523_CONTROL_2 0x01#define PCF8523_CONTROL_2_CTAF_BIT 6#define PCF8523_CONTROL_2_CTAIE_BIT 1#define ledPin 13 /* Attach a LED and resistor to this pin. LED is on when Arduino is awake, off when sleeping */#define sleepPin 0 /*must be an external interrupt pin */

I suggest you use a library to check if everything is working ok with it.https://learn.adafruit.com/ds1307-real- ... no-libraryThis library works with the PCF8523 as well. If everything is working you can revert to your code step by step until you find the part that is failing.

I don't think the RTC is the problem. If I comment out the sleep portion and set up a variable to count pulses on Pin 0 I can see the interrupts coming in as planned. I think my issue is the "wakeup" portion of the sleep mode.

On another note, I don't think the RTC library supports the interrupt pin on the PCF8523, at least in my looking through the github files (and limited experience in library functionality). That is why I am using PCF8523.h instead.

I can't tell if the last post was sarcastic or not. I was not trying to be dismissive of your suggestions and I am sorry if it came off that way. I dug through RTClib.h and RTClib.cpp again and did find functionality for Pcf8523SqwPinMode but I am unsure if it can go longer than 1 Hz and I am looking for 1 minute as I want the feather fona to sleep for more than a second. I do not see anything setting up the timers but again, I am a relative newb especially when it comes to libraries so maybe I am missing something. Is there an rtc.interrupt_timerA(); or similar function that I missed?

You have a pullup on pin 0. The sketch will sleep whenever pin 0 is high. So, your interrupt pulse goes low, the processor wakes up, and the interrupt is reset. Pin 0 goes high again, and you immediately go back to sleep. The LED probably does light up, but it's much too brief to see.